While many couplings or coupling devices have been utilized and even patented for joining steel reinforcing bars for use within concrete structures, the most common practice today continues to be the age old practice of merely tying the reinforcing bars together with a length of steel wire. Despite the many types of coupling devices that have been developed, this practice has persisted because it is a simple, quick and low cost method of effecting the coupling. In this practice, the reinforcing bars, more commonly referred to as "rebars" in the trade, are merely laid end-to-end with their close ends overlapping for about four inches or more. Then a stiff wire is merely wrapped tightly around the overlapped ends with a number of turns extending the length of the overlap.
With reference to the coupling devices patented, examples can be found in U.S. Pat. Nos. 3,390,905; 3,694,012; 3,782,839; 4,114,344; and 4,143,986 each of which comprise multiple components which must be bolted, threaded, keyed or welded together, either in fabrication of the device, or as a necessary step to effect the coupling of the two rebars. While all of these couplings would obviously suffice to effect the coupling as disclosed in those patents, all but one are designed to effect an end-to-end coupling as opposed to an overlapping coupling. Most building codes and construction specifications require that the ends of the rebars coupled together within reinforced concrete have a four to five inch overlap to assure that there is no plane of reduced tensile strength where the concrete could crack through between opposing ends of the rebars. Such coupling devices that do not provide for the required overlap would not be permitted under these codes and specifications. Moreover, all of the coupling devices disclosed in the above cited patents, require that the worker making the coupling, have direct manual access to the coupling itself in order to effect the coupling.
In many applications where steel reinforcing bars are utilized to reinforce concrete structures, it is only natural that the connections, whether wire tied or by coupling device, be effected by direct manual access to both the coupled ends of the rebars and the coupling device or wire. In one application at least, however, it would be highly desirable if such a coupling operation could be effected remotely to at least one end of a rebar by handling and manipulating the other end thereof. Specifically, in many large buildings or structures built of large concrete block walls, codes and/or construction specifications require that the holes through the concrete blocks be aligned vertically over one another so the the holes will extend for the full height of the block wall, and further require that those holes be filled with concrete having at least one continuous or coupled strand of steel reinforcing bar running the full height thereof. When this is required, the procedure for laying the concrete blocks becomes very complicated and cumbersome, causing the block laying rate to be greatly reduced, by as much as 90%. This of course, not only adds to the time required for construction of the wall, but also adds greatly to the cost.
The reason for the great amount of time and cost required for erection of a concrete block wall having steel reinforced concrete therein, becomes apparent when the procedures for erecting such walls are known. In this procedure, the concrete foundation or footer under the concrete block walls must first be poured over prepositioned rebars so that short lengths of rebars, say ten to twelve inches, extend upward through the upper surface of the concrete, and there aligned so that one rebar each will extend upward through each hole of the concrete blocks as they are laid to form the first course of the concrete block walls. After the first course of concrete block have been so laid, another length of rebar is secured to each short length of rebar extending upward through the row of holes along the top of the concrete block course. It is normally required that there be a four or five inch overlap where the two pieces of rebar are joined. Therefore, they are usually joined together by wrapping their overlapped ends with a length of stiff steel wire, as described above. Thereafter, as additional courses of concrete block are laid, each block must have its end buttered with mortar for the vertical joint, and then the block must be lifted to the top of the vertically oriented rebars and then lowered so that the appropriate rebars are threaded up through the holes in the block. Should the buttered wet mortar fall from the end of the block during this operation, it must be lifted back free of the rebars and rebuttered, as codes do not normally allow the joints to be mortared after the block is in place.
When sufficient courses of concrete block have been laid that there are just short lengths of rebars remaining above the top edge of the blocks, it is of course necessary to couple additional lengths of rebar to the upper ends of those in place if the block laying is to continue. For very tall walls, it will be necessary to repeat this procedure several times so that each vertical hole through entire height of the concrete block wall may contain several lengths of rebar coupled in line. After the final course of blocks have been laid, fresh concrete must be poured down into each hole so as to surround each length of rebar with concrete for the full height of the wall.